Traveling to your next destination by plane may be the quickest way to get from point A to point B, but there’s no denying there are many, many things that air travel leaves to be desired.

Like having to get to the airport hours before boarding, struggling with baggage size and weight limits and attempting to battle the near unstoppable desire to buy a new novel and three magazines before each and every flight.

But all those things pale in comparison to the four letters that can delay your next trip to the airport an absolute nightmare.

Travellers who see the letters ‘SSSS’ on their boarding passes face extra security and screening measures before they are able to board a flight.

The code stands for ‘Secondary Security Screening Selection’ and means a passenger faces additional screening by security which could take an extra half hour.

The term only appears on the passes of those travelling to the United States, but with the US among the top destinations for Aussie travellers, the code is one many holidayers have faced.

According to The Sun, the code was introduced to reduce the risk of terror attacks and involves Transportation Security Administration (TSA) agents subjecting passengers to extra pat downs, swabs and bag searches.

Passengers may also be asked to prove their identity and give officers a detailed run-down of their travelplans and itinerary.

The TSA has said that people are added to the list after being ‘randomly selected’ by a computer, but some passengers say they are branded with the SSSS code each and every time they travel.

The list is kept secret by the TSA and there is no way to check if you are on it, but buying tickets with cash or regularly buying one-way tickets could flag you as a potential security threat.

Passengers who have travelled to certain countries, like Turkey, may also face the prospect of SSSS showing up on their next boarding pass.